Migration from PetitParser

Why should you migrate to PetitParser2? If you find one of these interesting:

Actively Maintained

PetitParser2 is still actively maintained. By the author of PetitParser2 and by the Moose community.

Same as PetitParser

PetitParser2 can express everything PetitParser can and more. For example, there are predicates such as #startOfLine, #endOfLine, which are not available in PetitParser.

Better performance

The performance of PetitParser2 is 2-5 times better compared to PetitParser. The optimizations are based on our experience with PetitCompiler.

Try it out! Compare the optimized version of PP2SmalltalkParser, non-optimized version, SmaCC and RBParser. Evaluate the following code:

PP2Benchmark exampleSmalltalk

You can see that PetitParser2 is as fast as SmaCC while having all the advantages of PetitParser. PP2 parsers can be optimized by calling optimize method on the resulting parser.

Works with streams

PetitParser2 supports real streams: no need to load the whole input into the memory (see PP2BufferStream). Try to parse an input comming from your keystrokes. The following parser waits for the input from a keyboard does parsing as characters come in:

PP2ReadKeysExample example

If you want to use Zinc stream, try PP2HtmlHeaderGrammar, which can read headers of the web page, without downloading the whole page:

PP2HtmlHeaderGrammar example

Support for bounded seas

With PetitParser2 you can define only part of the grammar and skip the rest. With bounded seas you define islands of interest only. Bounded seas will skip the undefined input and return only islands. For example, you can easily extract JavaScript from HTML pages.

Support for context-sensitive rules

With PetitParser2 you can parse more languages than PEGs can express. PetitParser2 contains an extension for parsing context sensitive grammars.

Differences to PetitParser

How is PetitParser2 different to PetitParser? To increase performance, PetitParser2 decouples the parsing strategy from the parser structure while preserving the PetitParser interface. The parsing strategy is replaced behind the scenes and is mostly transparent for the end user.

The differences are:

• Parsers are subclass of PP2Node, not PPParser.
• Failure is instance of PP2Failure, not PPFailure. Failures are created using asPetit2Failure, not asPetitFailure.
• Terminal parsers are created using asPParser method, not asParser.
• Complex grammars are defined by subclassing PP2CompositeNode, not PPCompositeParser.
• Many other objects from PetitParser have their PetitParser2 equivalent with PP2 prefix.

Restrictions

• PP2CompositeNode does not support dependencies as PPCompositeParser. I am not aware of any use-case for dependencies, so I didn’t migrated the functionality. Let me know if there is a use-case for you.